本文選題：重味夸克 + 方位角關(guān)聯(lián)�。� 參考：《中國(guó)科學(xué)院研究生院(上海應(yīng)用物理研究所)》2017年博士論文

【摘要】：現(xiàn)有宇宙理論認(rèn)為宇宙“大爆炸”后的極短瞬間內(nèi)形成的超高能量密度能夠使得一種稱為“夸克—膠子等離子體”(QGP)的物質(zhì)在極短時(shí)間內(nèi)產(chǎn)生。格點(diǎn)QCD理論計(jì)算預(yù)言在極高溫度或者極高能量密度下,核物質(zhì)能夠發(fā)生強(qiáng)子態(tài)向夸克物質(zhì)態(tài)的轉(zhuǎn)變,部分子能夠從禁閉的強(qiáng)子相中解禁出來形成夸克-膠子等離子體。為了研究這種新型物質(zhì)形態(tài),物理學(xué)家建造了相對(duì)論重離子對(duì)撞機(jī)(RHIC),試圖在實(shí)驗(yàn)室中再現(xiàn)宇宙早期那種高溫高密的狀態(tài)。研究表明RHIC能區(qū)金核撞擊產(chǎn)生的溫度比太陽(yáng)表面溫度高出3億多倍。這樣的極端環(huán)境為探索強(qiáng)相互作用夸克-膠子等離子體和研究相變現(xiàn)象提供了有利條件。在相對(duì)論重離子碰撞中,重味夸克是QGP物質(zhì)性質(zhì)的敏感探針。重味夸克由于質(zhì)量大、產(chǎn)生早,經(jīng)歷了整個(gè)源介質(zhì)的演化過程,攜帶了大量初始時(shí)刻的特征信息。在RHIC能區(qū),重味夸克一般通過初始硬過程成對(duì)產(chǎn)生。一種研究重夸克在QGP介質(zhì)中能量損失機(jī)制的有效手段是測(cè)量重味夸克觸發(fā)的方位角關(guān)聯(lián)。理論研究表明重味關(guān)聯(lián)有助于揭示重味夸克-QGP介質(zhì)相互作用動(dòng)力學(xué)特征,區(qū)分重夸克在介質(zhì)中的能量損失機(jī)制。同時(shí),在高能質(zhì)子-質(zhì)子碰撞中測(cè)量重味夸克關(guān)聯(lián)則可以用于檢驗(yàn)微擾QCD理論計(jì)算并比較重夸克噴注碎裂強(qiáng)子化機(jī)制與輕夸克的差別。本論文主要研究了實(shí)驗(yàn)測(cè)量質(zhì)心系能量(?)=500 GeV下p+p碰撞中心快度區(qū)的D*介子與帶電強(qiáng)子方位角關(guān)聯(lián)和D*+-D*-方位角關(guān)聯(lián)。利用STAR 2011年運(yùn)行期間采集的p+p碰撞實(shí)驗(yàn)數(shù)據(jù),我們分析研究了觸發(fā)橫動(dòng)量6pT20 GeV/c區(qū)間D*介子與帶電強(qiáng)子的方位角關(guān)聯(lián),比較了D*-強(qiáng)子(D*-h)和雙強(qiáng)子(h-h)的關(guān)聯(lián)信號(hào)。研究表明D*-h關(guān)聯(lián)和h-h關(guān)聯(lián)在near-side(0△(?)π)區(qū)間具有顯著差別,主要表現(xiàn)為h-h關(guān)聯(lián)產(chǎn)額系統(tǒng)性地高于D*-h,關(guān)聯(lián)寬度小于D*-h。論文同時(shí)比較了實(shí)驗(yàn)測(cè)量結(jié)果和基于pQCD理論框架的PYTHIA模型模擬計(jì)算結(jié)果,發(fā)現(xiàn)基于pQCD理論框架的PYTHIA模型能夠很好的描述實(shí)驗(yàn)測(cè)量結(jié)果。在此基礎(chǔ)上,我們首次測(cè)量了p+p 500 GeV碰撞中D*+-D*-的方位角關(guān)聯(lián),并比較了PYTHIA的理論計(jì)算結(jié)果。目前在重離子碰撞中直接通過強(qiáng)子衰變道重建D介子并測(cè)量D介子觸發(fā)關(guān)聯(lián)信號(hào)具有很大挑戰(zhàn)性。傳統(tǒng)探測(cè)器的粒子徑跡動(dòng)量投影分辨率較低,在不變質(zhì)量重建中組合背景的貢獻(xiàn)極大,信號(hào)的顯著度很低。為了精確測(cè)量重味夸克,STAR實(shí)驗(yàn)組在2014年升級(jí)運(yùn)行重味徑跡探測(cè)器-Heavy Flavor Tracker(HFT)。HFT是一個(gè)高分辨率的硅像素探測(cè)器,可以實(shí)現(xiàn)粒子徑跡的高分辨率的測(cè)量,能夠精確地測(cè)量次級(jí)衰變頂點(diǎn)的位置,顯著減小組合背景貢獻(xiàn),極大地提高D介子測(cè)量的信噪比。HFT在2014-2016年運(yùn)行期間采集了大量數(shù)據(jù),有助于實(shí)現(xiàn)對(duì)重味強(qiáng)子總產(chǎn)生截面,重味夸克能量損失,重味夸克流和重味夸克觸發(fā)方位角關(guān)聯(lián)方面的精確測(cè)量。本論文工作還同時(shí)包括了重離子碰撞中各向異性流和初始偏心率漲落的唯象研究。利用AMPT(A Multi-Phase Transport Model)多相輸運(yùn)模型,我們系統(tǒng)地研究了質(zhì)心系能量為200 GeV的金核-金核碰撞中各向異性流和各向異性流的漲落。通過研究流的漲落跟碰撞的中心度關(guān)系,橫動(dòng)量關(guān)系以及贗快度關(guān)系,具體地分析了流的漲落特征。我們發(fā)現(xiàn)橢圓流(v2)在中心碰撞情形下主要由漲落貢獻(xiàn),相對(duì)漲落在非中心碰撞時(shí)具有贗快度依賴較大,而在中心碰撞時(shí)較小。同時(shí)還研究了三階流(v3)和四階流(v4)的相對(duì)漲落,發(fā)現(xiàn)v3完全由漲落貢獻(xiàn)且具有很小的中心度依賴性及橫動(dòng)量依賴性。進(jìn)一步考慮部分子散射和強(qiáng)子再散射的影響,發(fā)現(xiàn)部分子相互作用對(duì)于流的漲落影響很大,強(qiáng)子散射對(duì)于流的漲落影響很小,說明流的漲落主要起源于部分子階段。通過提取AMPT模型初始部分子階段的信息,我們系統(tǒng)性地研究了質(zhì)心系能量200GeV下金核-金核碰撞中的初始部分子偏心率和偏心率的漲落。部分子偏心率反映了高能核-核碰撞早期部分子空間的幾何形態(tài)特征,對(duì)于碰撞系統(tǒng)早期演化有著重要的影響。通過系統(tǒng)性地比較參與部分子偏心率εn{part}和多粒子累積矩偏心率εn{m}(m=2,4,6),發(fā)現(xiàn)Q-cumulant偏心率略小于常規(guī)累積矩偏心率,高階偏心率的漲落同對(duì)應(yīng)階流系數(shù)的漲落特征相似。我們同時(shí)還研究了高階流和偏心率的比例關(guān)系,并研究了轉(zhuǎn)變系數(shù)vn/εn的中心度、橫動(dòng)量以及贗快度依賴性,發(fā)現(xiàn)在中快度區(qū)轉(zhuǎn)變系數(shù)vn/εn高于前后向快度區(qū)。研究橫動(dòng)量關(guān)系比較了低橫動(dòng)量強(qiáng)子和高橫動(dòng)量強(qiáng)子的轉(zhuǎn)變效率的差別,發(fā)現(xiàn)在中低橫動(dòng)量區(qū)間轉(zhuǎn)變效率隨著橫動(dòng)量單調(diào)遞增。研究初始幾何漲落將有助于深入理解相對(duì)論重離子碰撞中QGP的演化圖像。
[Abstract]:The existing universe theory holds that the ultra high energy density formed in the very short instant after the "Big Bang" can produce a substance called "quark gluon plasma" (QGP) in a very short period of time. The lattice QCD theory predicts that at extremely high temperature or high energy density, the nuclear matter can occur to the quark in the hadronic state. In order to study the form of the new material, the physicist built the Relativistic Heavy Ion Collider (RHIC), trying to reproduce the high temperature and high density of the early universe in the laboratory in order to study the new form of the material. The study showed that the RHIC energy zone was produced by the collision of gold nuclei. The temperature of the birth is more than 300 million times higher than the surface temperature of the sun. This extreme environment provides a favorable condition for the exploration of the strong interaction quark gluon plasma and the study of the phase transition. In the relativistic heavy ion collisions, heavy quark is a sensitive probe for the properties of QGP. Heavy quark has been produced early, and has experienced the whole source. The process of qualitative evolution carries the characteristic information of a large number of initial moments. In the RHIC energy region, heavy quarks are usually produced by the initial hard process. An effective means to study the energy loss mechanism of heavy quarks in the QGP medium is to measure the azimuth relation of heavy quark triggered. The kinetic characteristics of the interaction of the gram -QGP medium can distinguish the energy loss mechanism of heavy quark in the medium. At the same time, the measurement of the heavy quark Association in the high energy proton proton collisions can be used to test the perturbation QCD theory and compare the difference between the heavy quark shotcrete and the light quark. This paper mainly studies the experimental measurement. The D* meson of the center of mass energy (?) =500 GeV is associated with the azimuth relation of the charged hadron azimuth and the azimuth of the charged hadron in the p+p collision center. Using the p+p collision experiment data collected during the operation of STAR in 2011, we analyze and study the azimuth relation between the D* meson of the trigger transverse 6pT20 GeV/c interval and the charged hadron, and compare the D*- hadron (D*-h). ) correlation signal with double hadron (H-H). The study shows that D*-h Association and H-H association are significantly different in the near-side (0) (?) PI interval, which mainly shows that the H-H associated yield is systematically higher than D*-h, the correlation width is less than D*-h., and the experimental measurement results and the PYTHIA model simulation results based on the pQCD theoretical framework are compared. The PYTHIA model of the pQCD theoretical framework can describe the experimental results very well. On this basis, we first measure the azimuth relation of D*+-D*- in the p+p 500 GeV collision and compare the theoretical calculation results of PYTHIA. At present, the D meson is rebuilt by the hadron decay path in the heavy ion collisions and the D meson triggers the associated signal. It is very challenging. The resolution of the particle track momentum projection of the traditional detector is low, the contribution of the combined background in the constant mass reconstruction is great, the signal's saliency is very low. In order to measure the heavy flavor quark accurately, the STAR experimental group upgraded the heavy track detector -Heavy Flavor Tracker (HFT).HFT in 2014 as a high resolution. The silicon pixel detector can measure the high resolution of the particle track. It can accurately measure the position of the secondary decay vertex, significantly reduce the combined background contribution, and greatly improve the signal to noise ratio of the D meson measurement.HFT during the 2014-2016 year operation, which helps to realize the total cross section and heavy quark of the heavy hadron. Energy loss, heavy quark flow and heavy quark triggered azimuth correlation are accurately measured. This paper also includes the phenomenological study of the anisotropy flow and the initial eccentricity fluctuations in heavy ion collisions. Using AMPT (A Multi-Phase Transport Model) multiphase transport mode, we systematically studied the mass of the mass of 200 G The fluctuation of anisotropic and anisotropic flows in the gold nucleus collisions of eV. By studying the relationship between the fluctuation of the flow and the centrality of the collisions, the relation of the transverse momentum and the pseudopotential, the fluctuation characteristics of the flow are analyzed. We find that the elliptic flow (V2) is mainly contributed by the fluctuation in the central collision, and the relative fluctuation is in the non central collision. At the same time, the relative fluctuations of the three order flow (V3) and the four order flow (V4) are also studied. It is found that the V3 is fully contributed by the fluctuation and has a very small centrality dependence and transverse momentum dependence. The effect of partial scattering and hadronic scattering is further considered, and the interaction of partial subgroups is found. The fluctuation of the flow has a great influence. The scattering of hadrons has little influence on the fluctuation of the flow. It shows that the fluctuation of the flow mainly originated from the partial substage. By extracting the information of the initial partial substage of the AMPT model, we systematically studied the initial partial eccentricity and the eccentricity of the gold nucleus and gold nucleus collisions under the mass of the mass 200GeV. The molecular eccentricity reflects the geometric shape characteristics of the early part of the high energy nuclear nucleus collisions, and has an important influence on the early evolution of the collision system. By systematically comparing the partial eccentricity rate epsilon n{part} and the eccentricity of the multi particle cumulative moment of epsilon n{m} (m=2,4,6), it is found that the eccentricity of the Q-cumulant is slightly less than the conventional cumulative moment eccentricity. The fluctuation of the higher order eccentricity is similar to the fluctuation of the corresponding order flow coefficient. At the same time, we also study the ratio relation between the high order flow and the eccentricity, and study the center degree, the transverse momentum and the pseudopotential dependence of the transition coefficient vn/ e n. It is found that the transition coefficient vn/ n in the middle speed region is higher than the front and back region. The difference between the transition efficiency of the low transverse momentum and the high transverse momentum hadrons shows that the transition efficiency of the middle and low transverse momentum increases monotonically with the transverse momentum. The study of the initial geometric fluctuation will help to understand the evolution image of the QGP in the relativistic heavy ion collisions.
【學(xué)位授予單位】：中國(guó)科學(xué)院研究生院(上海應(yīng)用物理研究所)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2017
【分類號(hào)】：O572.33;O572.214

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